Your breastmilk is the best possible food to help your baby grow and develop, combined with antibodies, live cells, and other substances to protect him from infection. It’s worth the effort to provide expressed milk for your baby when you can’t be there to nurse him. Although some of the nutrients and anti-infective properties change with storage, expressed milk is still much better nutritionally for your baby than infant formula. This page gives guidelines on storing your milk.
Storing breastmilk for healthy full-term babies
How much milk will I need?
Preparing to use
Keeping milk for the next feed
Away from home
Different storage times
Illness in the family
Storing breastmilk for healthy full-term babies
Breastmilk’s antibacterial properties help it stay fresh. The live cells and antibodies that discourage the growth of bacteria in your baby’s intestines also guard against bacterial growth when your milk is stored in a container.
The guidelines that follow apply to milk that will be given to full-term healthy babies. If your baby is premature or sick, hospital staff can give you information on stricter storage guidelines, to ensure your baby gets as much benefit from your milk as possible.
Good hygiene is important when storing your milk. Reduce the risk of contaminating your milk by:
- Washing hands before expressing or handling milk
- Keeping your pump clean, using hot soapy water for all parts which come into contact with your milk. Some mothers sterilize as well
- Keeping your fridge, freezer, coolbag and icepacks clean
- Placing containers of milk in a clean bag or lidded box before storing
- Keeping your milk away from meat, eggs, etc
Hard-sided containers, either glass or plastic, do the best job of protecting your breastmilk. Avoid containers made with the controversial chemical bisphenol A, identified with a number 3 or 7 in the recycling symbols. A safer alternative is polypropylene, which is soft and semi-cloudy and marked with a 5 or letters PP.
- Use containers with well-fitting tops
- Wash containers in hot, soapy water, rinse well, and allow to air-dry before use. Or wash and dry in a dishwasher
- Leave 2.5cm of space at the top to allow the milk to expand as it freezes. Plastic milk storage bags, designed for freezing breastmilk are convenient and take up less room in the freezer
- Avoid bags that are not designed for freezing—they may burst or tear. Double bagging can prevent accidents
- Some milk storage bags can be attached directly to a breast pump, so you can collect and store milk in the same container
- Allow 2 to 3 cm for the milk to expand when frozen and squeeze out the air at the top before sealing
- Stand the bags in another container on the fridge shelf or in the freezer
Store milk in 60 to 120ml (2 to 4 oz) quantities to avoid waste, at least until you know how much milk your baby takes at a feed. Small quantities thaw quickly and can be combined if needed. You can also store smaller quantities of 30ml for when your baby is extra hungry, or wants to be fed just before you’re due back.
You can combine milk pumped at different times, if you:
- Cool fresh milk for 30 minutes in the fridge first
- Add fresh milk to frozen milk only if there is less fresh milk than frozen
- Use it within the time limit of the oldest expressed milk
Looks are deceptive!
It’s perfectly normal for expressed milk to look thin, bluish, yellowish or even brownish in colour and for it to separate into a milk layer and a cream layer when stored.
Thaw and heat with care
High temperatures or even moderate temperatures over a period of time affect many of the beneficial properties of breastmilk, so:
- NEVER warm breastmilk in a pan on a cooker
- NEVER warm breastmilk in a microwave
Microwaves do not heat liquids evenly, so there may be hot spots in the container of milk, and this can be dangerous for babies.
Defrosting frozen breastmilk Your milk can be defrosted in the fridge, avoiding unnecessary heating. Use within 24 hours.
To defrost your milk more quickly:
- Hold the container under cool running water and gradually increase the temperature of the water to heat the milk to feeding temperature, or;
- Immerse the container in a bowl of warm water. Take the milk out and reheat the water if necessary. Do not stand in a pan of water heating on the hob.
Refrigerated Milk: Warm for a few minutes under a tap or in a container of water. Test for temperature on the inside of your wrist.
Avoid contamination: Dry the containers before opening, with paper kitchen towels or a clean tea towel.
Breastmilk separates naturally: Gently swirl the container to remix.
Breastmilk is remarkably resilient – it stores well due to its antibacterial properties.
Store milk in the coldest part of fridge and freezer. Self-defrosting freezers can have warm spots. Use fridge and freezer thermometers to determine where the temperature is most constant. The fresher your milk, the better
Milk stored in the fridge will have more goodness than frozen milk. Some of the anti-infective properties are lost when milk is frozen—but it still helps protect babies from disease and allergies and is far superior to any formula. Although you probably won’t plan to keep your milk in the fridge for seven or eight days it’s good to know you can use safely any you find hidden at the back of the fridge. When your baby gets your milk within a few days of being refrigerated, it’s also reassuring to know it is well within its usable limits.
|Temperature (degrees C)||Best before||Use within|
|Freshly expressed milk - ideally refrigerate or cool immediately|
|warm room||19-26||4 hours||6 hours|
|cool bag or box with icepacks||15||10 hours||24 hours|
|cool bag or box with icepacks||4-10||24 hours||3 days|
|Refrigerated milk - longer storage times are safe if milk is collected in a very clean careful way and cooled immediately|
|Fresh milk||1-4||72 hours||8 days|
|Defrosted milk||1-4||as soon as possible||24 hours|
|Frozen milk - milk should not be refrozen|
|Freezer||variable temp around -18||3 months||6 months|
|Freezer||constant temp -18 or below||6 months||12 months|
It’s best to throw away leftover frozen or heated milk, which will have lost some of its antibacterial properties. It isn’t known how safe it is to keep fresh breastmilk left in the bottle after a feed. It should certainly be used within 1–2 hours. Avoid wasting precious milk by offering small amounts at a feed.
Expressed breastmilk can be kept in a common fridge at work or at the childcare centre. Label clearly. If a fridge isn’t available, place it in an insulated container with deep frozen ice packs. With enough icepacks, milk will stay at fridge temperatures for up to 24 hours. Icepacks are also useful when carrying milk home from work or to childcare, especially on warm days. But breastmilk can be safely refrigerated or frozen after short periods of storage at higher temperatures.
If you plan to store large amounts you could try freezing a small batch for a week before defrosting and tasting it. Some mothers notice their milk smells slightly soapy once defrosted, due to high levels of lipase, the enzyme that breaks down fat. The milk is still safe to use but some babies refuse to drink it. Heating milk to a scald (bubbles around the edges, not boiling) then quickly cooling it before freezing can deactivate the lipase.
Freezing deactivates yeast but doesn’t kill it, but there is no current evidence that milk frozen when you and your baby have thrush will reinfect you later.
There isn’t yet complete agreement about storage times. But it’s always preferable to store milk for as short a time as possible to ensure:
- Minimal growth of bacteria
- Minimal loss of antibodies and nutrients
Laboratory studies have shown that breastmilk becomes less resistant to bacteria with time, but most of the bacteria found in breastmilk are harmless skin bacteria and not illness-causing ones.
The longer you store your milk, the more care you need to take about
- Cleanliness while expressing, storing and handling milk
- Storing milk at appropriate temperatures (use fridge and freezer thermometers)
- Checking for bad taste and smell, which will show if your milk has gone off. Discard any milk that smells bad
If any family members are ill, especially with sickness and diarrhoea, your baby will be better off with fresh milk rather than frozen. The most recent milk from your stores will offer him the best protection from the illness. You may prefer not to freeze your milk until everyone is better.
Making it work
This information can help you decide how to store your milk to meet your needs. LLL meetings are a good source of support, whatever your reasons for expressing your milk. Or contact your local LLL Leader for one-to-one support.
Written by Karen Butler, Sue Upstone and mothers of La Leche League Great Britain
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Breastfeeding Answers Made Simple
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